Crystalline Insights
An X-ray Lab-Based Tutorial and
Structure Determination Demo
by Michael J. Vela, Tae H. Cho
and Bruce M. Foxman
This tutorial was
written with
the advanced high school science student in mind. Since most high
school
chemistry classes only briefly discuss aspects of crystal structure,
the goal
of this tutorial is to extend the subject to a demonstration of the practical
operations of X-ray diffraction and structure determination. While
it is
important to us that the tutorial be a stand-alone educational tool, we
hope
that, on suitable occasions, small groups of high school students,
accompanied
by their teachers, will visit Prof. Foxman’s
X-ray
lab (or another lab closer to home) for a field trip. In
preparation for
the trip, students would have completed some or all
of the
tutorial and have grown crystals of citric acid or sucrose. A
suitable
crystal would be selected from the batch, mounted on the diffractometer,
and solved in a few hours’ time. We believe this will provide an
enrichment opportunity for students and teachers alike. Version 1.01 of the tutorial contains >
110 PowerPoint
"slides", as well as a large number of external links.
Connection to the internet is not required to use the tutorial, as the
links
are included with the distribution.
In a
chemistry
course students learn about types of bonding, bond distances and
angles, Lewis
Dot Structures and VSEPR. How were the distance and angle values
determined? How do we know how the atoms are connected in a
molecule? Can we “see” atoms? The technique of X-ray
structure
determination provides both insight and answers to these
questions. This
practical tutorial is designed to show the operations involved
in taking
a crystal of a common compound, such as sucrose or citric acid, and
determining
its structure using X-rays. There are also slides, links, and
“side
trips” to help with some of the fine points. Going straight
through the
show, without the side trips, will provide an excellent idea of just
what an
“X-ray crystallographer” does every day (but do visit the “extras” for
the best
experience). Today, the technique of X-ray structure
determination is
extremely important in many fields, including chemistry, materials
science,
pharmaceuticals and the structure determination of
proteins.
Support
by the National Science Foundation through grants DMR-0504000 and
CHE-0521047
is gratefully acknowledged.
Version
1.01 INCLUDES ALL EXTERNAL LINKS. The inclusion of links was made
in
response to comments from users of the University-level Space Groups
and
Symmetry tutorial, available on this site, that
links
soon became outdated or changed. The “notes” section on each
slide
includes the complete references to the links bundled with this
version.
In order for the bundled links to run successfully, the tutorial must
be
installed in a specific directory (C:\insights). Full
instructions are
given below.
The tutorial will run
on a PC or
Mac with MS PowerPoint installed. The download is a compressed .zip
file.
Please fill in
these details
to help us track usage of the program. You will not be sent unsolicited
email.
You may be notified of important updates if you request them by leaving the
check in the box below:
Download Tutorial (Insights.zip,
Compressed Version, 28.9 Mb)
Once the .zipped file
above has
been downloaded, the tutorial must be installed in the specific
directory
“C:\Insights”. A shortcut provided in that directory may
then be
moved to the desktop if desired, or the program may be run directly
from the
directory by double-clicking on the shortcut in the directory.
Note that the folder "Main" must appear
at the top level of the Insights directory, or all links will be broken.
The
tutorial contains historical and pedagogic links; browser behavior
varies with
version and "brand". Returning to the tutorial from the browser
seems to work best in Mozilla/Netscape by
minimizing
the browser window. In IE, return to the tutorial works best
using a
right-click, and selecting "Back". Let us know if there are any
problems. The
tutorial
links have been tested with only the latest versions of browsers. If erratic behavior is
encountered,
that is a source to consider.
There is a price for
using this
tutorial!!!! Please send feedback with corrections, suggestions, etc.
We hope
you will enjoy this material and will find it useful.
Many thanks!
Michael J. Vela
Brandeis University
Send content and tutorial comments to
Bruce M. Foxman ( foxman1 at
brandeis.edu)
Bruce Foxman
( foxman1 at brandeis.edu ) Last
updated 16 February 2007